Pulsar observations with LOFAR

Transcript

1. Radio pulsar surveys with LOFAR Joeri van Leeuwen (ASTRON) +

   PWG

2. Introduction 1 second of Crab-pulsar data with WSRT+PuMaII

3. Galactic longitude (degrees) 270 -500 0 z (pc) 500 180

   90 0 Why look for more pulsars? Young pulsars tell about birth location, velocities supernova mechanism Known proper motions of pulsars younger than 1Myr (Hobbs et al. 2005)

4. 12 13 11 -2 -1 0 1 Log period (s)

   Log magnetic field (G) Why look for more pulsars? Number of dim pulsars reveals supernova rates and minimum masses Clarify why long-period pulsars stop emitting Pulsar period versus magnetic field

5. Why look for more pulsars? Pulsars 'time' the relativistic effects

   caused by a possible companion (neutron star / black hole) measures masses and spin pulse arrival time residual (µs)

6. Why look with an interferometer? Time-based (vs. image-based) astronomy uses

   beam-forming, not interferometry Field of view dictated by largest separation, but sensitivity by total area: sparse Potentially form many parallel beams each with own periodicity-search back end Computationally challenging 8GR8; LOFAR; SKA (cf. Backer 1999)

7. Why look with an interferometer? Beam-forming pulsar survey WSRT, at

   ~1000 beams First ever pulsars discovered from NL Can find ~10s of new pulsars 28 28.5 29 29.5 30 30.5 292 292.5 293 293.5 294 294.5 295 295.5 DEC (deg, J2000) R A (deg, J2000)

8. LOFAR Pulsar survey Trade off between large FoV and high

   sensitivity. Supercore/core/entire LOFAR Different sparseness and total area

9. LOFAR Pulsar survey Theoretical gains Core, coherent: 8.8 K/Jy Core+NL

   incoherent: 1.8 K/Jy Supercore: 2.9 K/Jy van Leeuwen & Stappers (2009)

10. LOFAR Pulsar survey First station beam forming & tracking at

    Pulsar Busy Week Nov09:

11. LOFAR Pulsar survey Theoretical gains Pointings for all-sky Core, coherent:

    8.8 K/Jy 3.000.000 @ 2min Core+NL incoherent: 1.8 K/Jy 1.000 @ 1hr Supercore: 2.9 K/Jy van Leeuwen & Stappers (2009)

12. LOFAR Pulsar survey Simulate birth rates, evolution, selection effects for

    1e7 pulsars and 8 surveys: Survey Real Sim Jodrell (1972) 51 20 UMass-Arecibo (1974 50 39 MolongloII (1978) 224 227 UMass-NRAO (1978) 50 54 Parkes II (1991) 298 335 Cambr 80MHz (1993) 20 27 Parkes MB (1999) 1005 801 LOFAR (2009-2011)

13. LOFAR Pulsar survey Simulate birth rates, evolution, selection effects for

    1e7 pulsars and 8 surveys: Survey Real Sim Jodrell (1972) 51 20 UMass-Arecibo (1974 50 39 MolongloII (1978) 224 227 UMass-NRAO (1978) 50 54 Parkes II (1991) 298 335 Cambr 80MHz (1993) 20 27 Parkes MB (1999) 1005 801 LOFAR (2009-2011) 1200

14. LOFAR Pulsar survey Relatively robust; different luminosity and gain models:

15. LOFAR Pulsar survey Surveyed volume limited by multi-path scattering on

    ISM. van Leeuwen & Stappers (2009)

16. LOFAR Pulsar survey Can however see all radio pulsars within

    ~2kpc -10 5 10 0 position (kpc) 15 -5 0 position (kpc) 5 10 Lofar detection Sun Galactic Centre -2 -1 position (kpc) 0 position (kpc) 2 1 -2 -1 0 2 1

17. LOFAR Pulsar survey Can see very far out of galactic

    plane birth velocities: supernova kicks

18. LOFAR Pulsar survey Measuring velocities, ages, magnetic fields, etc takes

    pulsar timing Initial positions: run incoherent beam forming + 10ms per second correlation in parallel Optimizing detected pulsars within station beam: 44% of pulsars are in pairs in station beam -- 20% in triples -- 19% in 4+ Coherent beamforming on those: 10hr total to get detection SNR on all sources

19. Conclusions Computationally overcoming interferometer draw-backs (cf. SKA). Can find entire

    local population and measure velocity distribution infer supernova mass ranges, energetics